Rose Clover (Duke, 1981; McLeod, 1982).

Trifolium hirtum All (Duke, 1981).

Several varieties are available including 'Hykon,' 'Kondinin,' California Common ('Wilton') (Slayback, pers. comm.). According to Miller et al. (1989), 'Hykon' is the earliest maturing, and 'Kondinin' the most tolerant of soil acidity. 'Wilton' is the latest maturing and adapted to areas with greater than 14" annual rainfall. Graves et al. (1986) stated that 'Hykon' and 'Kondinin' (early maturing varieties) did well under San Diego County dryland conditions where 'Wilton' is not recommended.

The seed is yellowish, smooth, a little over 1/16th inch long, and has a scar on the end. Faint lines on the seed, that meet at the scar end, can be seen with a hand lens (Love and Sumner, 1955).

Numbers of seeds per pound for the various cultivars are as follows: 'Hykon' 135,000; 'Kondinin' 165,000, 'Olympus'; and 'Wilton' 140,000 (Murphy et al., 1976).

Rose clover, like various other legumes, produces "hard seed," with seedcoats preventing intake of water, and delaying germination for up to several years. This ensures that the seedbank is not depleted for some time, although weather during successive years may not permit reproduction (Murphy et al., 1976).

According to Love (1985), seed remain hard so long as they are held in the dried flower heads. Some seeds become germinable if the heads shatter and the seed are deposited on the ground. Many seeds remain impermeable even after passage through grazing animals.

Rose clover seedlings show good vigor (Slayback, pers. comm.).

During establishment, the force produced by legume seedlings may be crucial in overcoming the weight of overlying soil and surface crusts. Williams (1956) used glass tubes containing vermiculite and glass rods of known mass to estimate the force produced by seeds of crimson clover, rose clover, subterranean clover, and alfalfa. Mean forces exerted (in g, + SEM) were estimated as follows. Alfalfa: 15.2 + 0.5 g; crimson clover: 23.8 + 0.2; rose clover 24.1 + 0.5; subterranean clover 60.0 + 2.9. The force exerted by the seeds was highly correlated (R=0.999) with seed weight, but not so highly (R=0.837) with hydrolyzable carbohydrates, suggesting that other factors may operate, as well.

Rose clover is villous annual legume, with stems 1-4 dm tall, erect or ascending, with branches widely spreading (Duke, 1981). It is an upright branching clover with light-green leaves covered with dense, short hairs, and a 'watermark" of white or reddish-brown, either a spot or a crescent; flowers are rose-colored, globular, with abundant, soft hairs (Murphy et al. 1976).

Love and Sumner (1955) described the spreading branches as being densely covered with short, coarse hairs. As with most true clovers, each leaf has three leaflets at equal distances from the end of the leaf stalk, the center one somewhat larger than the other two. These leaflets are about the size and shape of those on bur clover, have a scattering of short hairs, over both surfaces, and usually a small, reddish mark a little above the center. The leaf stalks are from 1/2 to 2 inches long and have hairs like those on the leaflets. At the bases of the leaf stalks are hairy stipules 1/4 to 1/2 inch long, with smooth margins and ling, tapering points. The flower heads are rose-colored, spherical, about 3/4 inch across, and profusely covered with stiff, white hairs. A leaf with somewhat smaller leaflets grows directly from the vase of the flower head, and the stipule of this leaf cups up around the base of the head, as is the case for red clover.

Duke (1981) listed the species as tolerating mean annual temperatures from 14.1-19.7 degrees C, with a mean of 6 cases of 17.4).

McLeod (1982) stated that no other introduced legume is as well adapted to such a wide variety of climatic conditions, and paradoxically asserted that the plant is not winter hardy, yet is seldom injured by late spring frosts (McLeod, 1982).

Graves et al. (1986) stated that this species germinates as well as other legumes in cold, fall weather, but is a much better competitor if it is growing well before the cold months of December and January.

According to Duke (1981), rose clover orginated in the Mediterranean and Near Eastern Centers of Diversity, and is native to the western and eastern Mediterranean regions, Balkans, Asia Minor, Crimea, Caucasus, and the Transcaucasus. It ranges from the Warm Temperate Thorn to Dry through Subtropical Dry to Moist Forest Life Zones. It tolerates grazing, high pH, low pH, poor soil, and slope.

In the U.S., it grows in the southern states and California. (McLeod, 1982), yet it has not been used much for pasture in the southeastern states (Duke, 1981). In California, rose clover is variously listed as ranging to elevations as high as 3,000 ft. (Finch and Sharp, 1983; Graves et al., 1986), 3,300 feet. (McLeod, 1982), and 3500 feet (Slayback, pers. comm.). Munz (1973) reported that rose clover has been cited as a weed in Butte County.

'Hykon' has done well under San Diego County dryland conditions (Graves et al. 1986).

Rose clover does best in reseeding stands where broadleaf filaree, Erodium botrys, does well (Love, 1985).

Duke (1981) reported that rose clover tolerates a mean annual precipitation of 4.4-11.6 dm, with a mean of 20 cases of 7.0. Apparently due to its greater rooting depth (Love, 1985), it is also said to tolerate drier conditions than subclover (Love, 1985; Graves et al. 1986). On shallow range soils, rose clover exhausts soil moisture to a depth of about 1 m, preventing the emergence of summer weeds (Love, 1985).

According to Murphy et al. (1976), rose clover can survive with 10 inches of rain annually, but produces better with more. Rainfall requirements are variously given as 10 (McLeod, 1982), 12 (Munoz & Graves, 1988), and >14 inches per year (for cv 'Wilton') (Miller et al., 1989).

Murphy et al. (1976) indicated that rose clover cultivars should be able to reseed given the following minimum annual rainfall amounts:

• 'Olympus', 10 inches
• 'Hykon', 12 inches
• 'Kondinin', 12 inches
• 'Wilton', 15 inches

Duke (1981) stated that fertilizer requirements are minimal for rose clover and that it is tolerant of poor soils. Rose clover does better on infertile sites than do subterranean clovers (Love, 1985).

Applications of superphosphate (300 lbs/acre) increased forage production over 300% and protein content 70% in Placer County trials (Johnson et al., 1956).

Duke (1981) lists the pH range as 5.5-8.2, with the mean of 6 cases being 6.8. Love (1985) gave the range as 5.0-8.3. Rose clover does well on strongly acid to moderately alkaline soils, but does best if pH ranges between 6 and 7; it is less tolerant of low pH than are subterranean clovers (Graves et al., 1986).

'Kondinin' is the most acid-tolerant cultivar of rose clover (Miller et al., 1989).

Rose clover is tolerant of a wide range of soil types including infertile soils (Duke, 1981; Miller et al. 1989) but does not endure waterlogging. Sand to loam soils are best (Munoz & Graves, 1988). It grows "in dry, sterile fields, on slopes, on sandy steppes, on roadsides, in waste places in the Mediterranean region" (Love and Sumner, 1955), and does better on infertile sites than do subterranean clovers (Love, 1985). Murphy et al. (1976), McLeod (1982), and Graves et al. (1986) emphasized the importance of well-drained soils. Rose clover can survive poor, rocky soil and is usually a good forerunner to other clovers on low-fertility soils; it produces well under better soil conditions (Murphy et al. 1976). No other introduced legume is as well adapted to such a wide variety of soil types, according to McLeod (1982), who further stated that it will grow on poor soils where few other plants survive. Rose clover does best in reseeding stands where broadleaf filaree, Erodium botrys, does well (Love, 1985).

Published work from Univ. Calif. by Bud Kay ca. 1978 showed a tolerance to 2,4-D by both rose clover and subclover. (Fred Thomas, pers. comm.)

This cool-season annual starts growing in the winter and puts on most of its growth in the spring (Finch and Sharp, 1983), flowering during April and May (Munz, 1973), and seed maturing in May (Finch and Sharp 1983).

According to Love (1985), rose clover has a high percentage of hard seed, which remain so as long as seed are retained in the dried flower heads. Some seeds become germinable if the heads shatter and the seed are deposited on the ground but many remain impermeable even after passage through grazing animals.

Seeding rates are given as:

1. 1 to 10 lbs/acre whether solely or with a cereal. A seeding of 1 lb/acre can yield a solid stand in four or five years. The high rate should provide a solid stand the second year (Love and Sumner, 1955).
2. 6 lbs/acre (pure live seed) (Slayback, pers. comm.).
3. 9 lbs/acre (Finch and Sharp, 1983).
4. A minimum of 9 lbs/acre of raw seed, and up to 20 lbs/acre if seedbed is poor (Graves et al. 1986).
5. 15 to 20 lbs/acre (McLeod, 1982; Miller et al., 1989).
6. 17-22 kg/ha (Duke, 1981).
7. 15-30 lb/acre (Munoz & Graves, 1988).
8. 5 kg/ha if drilled, and 10-15 kg/ha if broadcast (Love, 1985).

Sow rose clover at 1/2 inch depth (Slayback, pers. comm.).

The best method for establishing rose clover is by drilling (Slayback, pers. comm.). A firm seedbed is desirable (Finch and Sharp, 1983), but a minimum of seedbed preparation is required.

According to Love and Sumner (1955), disk the field before the fall rains. After seeding, roll the area with a ring roller, then drill or broadcast the seed. If rose clover is to be seeded with a cereal, two methods apply: (1) seed the cereal first, then seed the rose clover by airplane; or (2) have an alfalfa drill attached to the grain drill and seed the cereal and clover at the same time.

Doves, quail, and robins feed on and disperse the seed of rose clover (Love, 1985).

Rose clover may be seeded from September to October 15 (Slayback, pers. comm.); early fall is best (Love and Sumner, 1955; Finch and Sharp, 1983; Munoz & Graves, 1988).

Rose clover requires the "WR" rhizobial inoculation type (Nitragin Company) (Burton and Martinez, 1980; Duke, 198l; Munoz & Graves, 1988).

According to Love (1985), two strains of rhizobia, "R" and K10, are effective on rose clover.

Rose clover seed is readily available; the species is grown for seed in California (Slayback, pers. comm.).

Munz (1973) listed flowering in April and May. Murphy et al. (1976) stated that 'Olympus' flowers in February, that 'Hykon'flowers 1-2 weeks after Olympus, 'Kondinin' 3-4 weeks after Olympus, and 'Wilton' 5-6 weeks after Olympus.

Rose clover matures in May (Graves et al., 1986), when seed is set (Miller et al., 1989).

Miller et al. (1989) listed 'Hykon' as the earliest-maturing cultivar and 'Wilton' as the latest.

Seed yields of rose clover range from 300-500 kg/ha (Love, 1985); seed will develop under unfavorable conditions (Love and Sumner (1955), including low moisture and soil fertility regimes (Murphy et al., 1976).

Reseeding is reliable (McLeod, 1982; Finch and Sharp, 1983), especially if rose clover allowed 3 to 4 weeks to regrow after mowing to set and mature seed (Finch and Sharp, 1983).

A high percentage of seed is hard (Love and Sumner, 1955).

The seed of rose clover remains viable for a relatively long time (McLeod, 1982).

Cv 'Olympus' has a prostrate growth habit, whereas 'Hykon' shows semi-erect growth and 'Kondinin' upright growth (Murphy et al., 1976). Duke (1981) described rose clover stems as 1-4 dm tall and erect or ascending, with branches widely spreading.

Height of rose clover has been variously mentioned as 3 to 18 inches high (Love and Sumner, 1955), 8 to 12 inches in height (Finch and Sharp, 1983; Graves et al., 1986), 1-4 dm (3.94 - 15.75 inches) (Duke, 1981), and 24 inches (Slayback, pers. comm.).

In Hopland, Mendocino County, California, cv 'Hykon' reached a height in early May of 43.18+/-3.28 cm (17 +/- 1.29 inches) (Mean +/- S.E.M.) (Bugg et al., unpublished data).

Due to its greater rooting depth, rose clover is more drought tolerant than subterranean clover (Love, 1985). The species is taprooted (Slayback, pers. comm.), and the taproot attains depth of up to 2 m (Street, cited in Love, 1985; Love, 1985).

During establishment, the force produced by legume seedlings may be crucial in overcoming the weight of overlying soil and surface crusts. To estimate the force produced by seedlings of crimson clover, rose clover, subterranean clover, and alfalfa, Williams (1956) used glass tubes containing vermiculite and glass rods of known mass. Mean forces exerted (in g, + SEM) were estimated as follows. Alfalfa: 15.2 + 0.5 g; crimson clover: 23.8 + 0.2; rose clover 24.1 + 0.5; subterranean clover 60.0 + 2.9. The force exerted by the seeds was highly correlated (R=0.999) with seed weight, but not so highly (R=0.837) with hydrolyzable carbohydrates, suggesting that other factors may operate, as well.

Rose clover reseeding is reliable (Graves et al., 1986).

Rose clover has a high proportion of hard seed relative to crimson or subterranean clovers, which allows it to dominate formerly-mixed stands following several years of drought (Williams and Elliott, 1960).

High temperatures at the soil surface and slightly above were demonstrated to cause breakdown of rose clover impermeability (Williams and Elliott, 1960).

In general, rose clover recovers well following mowing (McLeod, 1982), and it can be mowed to a height of 2-4 inches throughout the growing season (Miller et al., 1989).

Graves et al. (1986) provided the following provisos: mow at a height of 4 inches during the growing season to control competing vegetation, but allow a 3 to 4 week regrowth period after mowing to set and mature seed. Early- flowering varieties should not be mowed after late March. Following seed set in late May, mow at any height to eliminate summer weeds. The late mowing deposits seed on the soil to permit reestablishment the following fall.

Grazing on rose clover, which produces flowers at the ends of stems, must be regulated to keep animals from removing all the flowers (Murphy et al., 1976).

Christensen (1971) stated that for Californian vineyards, French plowing leaves a narrow strip of cover crops in each alley and would permit use of early-maturing species like rose clover. Dates for plowing down cover crops depend on the maturation dates: mid-May for rose clover.

Harvesting is by combine; yields range from 300-500 kg/ha (Love, 1985).

Harvesting is by combine (Love, 1985).

Uses include forage, cover crop, erosion control, and green manure (McLeod, 1982). Munoz & Graves (1988) recommended rose clover for erosion control, self-seeding forage. Duke's (1981) account listed range and planting on denuded soil along roadways, dams, and chapparal after fires as the main uses for rose clover. Scott Steward (pers. comm.) includes rose and strawberry clovers in mixtures with various perennial grasses. These form self-perpetuating or regenerating stands in roadside prairie plantings tested at Hedgerow Farms by John H. Anderson (pers. comm.). Doves, quail, and robins feed on and disperse the seed of rose clover (Love, 1985).

Rose clover can also be used as a cover crop in orchards and vineyards (Finch and Sharp, 1983).

Rose clover does best in reseeding stands where broadleaf filaree, Erodium botrys does well (Love, 1985).

According to Slayback (pers. comm.), rose clover grows well with 'Blando' brome, 'Zorro' annual fescue. Finch and Sharp (1983) state that it can be seeded with subclover or black medic, but McLeod (1982) suggests growing it alone because it is a poor competitor with other species.

Finch and Sharp (1983) stated that on extremely infertile soil with almost no growth of native plants, rose clover should be used alone. If there is a fairly good cover of native weedy annual grasses and other types, use a mixture of 50% rose clover, 25% subclover, and 25% crimson clover. Bur clover is not recommended in this original mixture because if it is not already present on a range, it is probably not adapted to the local soil.

Spacial and temporal variation in soil and weather suggest that mixtures of subterranean and rose clovers be used (Love, 1985). Love and Sumner (1955) recommended mixtures of winter annual legumes is desirable because: (1) Seasons vary in California, and rose clover may do better one year, and subclover another, on the same site. (2) Soil variation will lead to rose clover occupying the poorer soil or better drained areas, while subclover will do well on the better soil or moister areas.

Williams (1963) reported that crimson clover (Trifolium incarnatum L., strain S. Australian commercial), rose clover (T. hirtum All., strain S.6), and subterranean clover (T. subterraneum L. cv 'Bacchus') were sown in pure plantings and in 1:1 mixtures of two species. Competition for light was assessed in relation to leaf area and leaf position in the canopy. Leaf area in 4-cm horizontal strata, leaf weight, shoot weight production, and light penetration through canopies were measured at intervals during the vegetative phase (i.e., through 99 days after sowing). Crimson and rose clovers held apparent initial advantages over subterranean clover, in terms of light-absorbing surface area of cotyledons and first unifoliate leaves, and because these leaves were elevated further from the soil surface. However, this situation changed with time. In paired sowings, crimson and subterranean clover became equally dominant over rose clover, while subterranean clover overtopped crimson despite the greater total leaf area of the latter. The most productive mixture (crimson clover + subterranean clover) was no more productive that the best species (crimson clover) in monoculture. Competition has other dimensions than those reported here, including the advantage conferred by hardseededness of rose clover, which enables it to dominate multispecific stands following droughts that kill seedlings of the other two clovers.

Biomass harvest on May 15-16, 1991 at Blue Heron Vineyard, Fetzer Vineyards, Hopland, Mendocino County, California, showed dry above-ground biomass data for cv 'Hykon' rose clover was 6.153+/-1.672 Mg/ha (mean +/-S.E.M.), and with weeds included, 8.130+/-2.198 Mg/ha (Bugg et al., unpublished data).

Nitrogen content estimates include 50-100 lb/acre (Munoz & Graves, 1988), and in unirrigated pasture, rose clover was estimated to add about 50-60 lb/a of nitrogen (Holland et al., 1969). Williams et al. (1974) (cited in Love, 1985) estimated N-fixation of vigorous stands to reach 98 kg N/ha. Yields in a vineyard trial in Hopland, assuming 12.6% protein (Williams et al., 1957) and 6.25% of that protein being N, suggest an above-ground N content of 48.45 +/- 13.17 kg N/ha (mean +/- SEM) (R.L. Bugg, pers. comm.).

Red clover may be used for erosion control (Munoz & Graves, 1988), and Love and Sumner (1955) considered it the best winter annual-legume for reclaiming abandoned grain land.

According to Love and Sumner (1955), rose clover gradually improves soil, permitting growth of desirable forage plants. They cited the example of a ranch in Santa Clara County where the soil had become very thin, and would not support vegetation. The soil was improved through the use of rose clover, which built up the depleted nitrogen supply.

Cattle, sheep, and deer graze rose clover even when it is completely dried. Doves and quail also feed on the plant. Protein content of rose clover is slightly less than that of bur clover at similar stages (Love and Sumner, 1955).

Unlike some varieties of subterranean clover, rose clover contains neligible amounts of estrogens, and no reproductive disorders have been observed in sheep that have been fed it (Love, 1985).

Protein content of rose clover is less than for bur clover: 24.9 in lush vegetative stage, 12.6 at flowering, and 8.0 when dead ripe (Williams et al., 1957).

Cattle will avoid rose clover when green in favor of subclover or medics or other forages. (Fred Thomas, pers. comm.)

Flowering rose clover harbors abundant minute pirate bug (Orius tristicolor), an important beneficial insect (Bugg, pers. comm.), but can also harbor abundant lygus bug (Lygus hesperus), a pest of some crops (Rachid Hanna, pers. comm.).

Meloidogyne incognita acrita and M. javanica were reported in Duke's (1981) summary.

Whitehead (1992) stated that in a pot study, burr medic and several other annual Medicago spp. (e.g. barrel medic) showed good resistance to the lucerne (alfalfa) race of stem nematode (Ditylenchus dipsaci). Subterranean clover was deemed very resistant, rose clover resistant, and berseem susceptible.

Poor performance of rose clover in damp north-coast locales may be due damping-off disease, often caused by Pythium fungi (Murphy et al., 1976).

Rose clover is a poor competitor. Mowing at a height of 2 to 4 inches during winter will control weeds (Finch and Sharp, 1983).

Bugg et al. (unpublished data) found that in vineyard plots seeded in October to cv 'Hykon,' above-ground weed biomass the following May was 1.977+/-0.992 Mg/ha, Mean +/- S.E.M., which was 40.2% of the figure obtained in weedy control plots, and was the second highest absolute weed biomass figure observed for the 15 cool-season annual legumes assessed (although the observed differences were not statistically significant). In the winter-annual legume category, only cv 'Dalkeith' subterranean clover showed a higher absolute weed biomass. Dominant winter annual weeds were chickweed, shepherds purse, rattail fescue, and an annual ryegrass, probably darnel (Lolium temulentum L.). In early May, cv 'Hykon' had attained 83.75+/-8.00% (Mean +/- S.E.M.) vegetational cover (Bugg et al., unpublished data).

On shallow range soils, rose clover exhausts soil moisture to a depth of about 1 m, preventing the emergence of summer weeds (Love, 1985).